18.1. Biodiversity Flashcards
Species
a group of organisms with similar morphology and physiology, which can breed together to produce fertile offspring and are reproductively isolated from other species
Problems of the definition of Species
- Asexual reproduction? - no breeding
- Genetic Sequencing?
- Dogs with dissimilar morphology can reproduce - Chihuahua and Great Dane
Ecosystem
a relatively self-contained, interacting community of organisms, and the environment in which they live and with which they interact.
- A self-sustaining unit consisting of abiotic and biotic factors interacting together
- Includes all organisms of all populations (in a given area)
- Energy flows through and cycling of minerals occur
Examples of Ecosystem
- Tropical Rainforests
- Rivers
- Coral reefs
- Woodland
- Sandy desert
Niche
The role of an organism in the ecosystem. It includes where it lives and how it obtains its energy
Biodiversity
Degree of variation of lifeforms in an ecosystem
Biodiversity is made up of:
1) The number of species and their relative abundance
2) Genetic variation within each species
3) Variation in ecosystem or habitats
Species Diversity
- The variety of species within a habitat or a region, and the abundance of the different species
- Some habitats, such as rainforests and coral reefs, have many species. Others, such as salt flats or a polluted stream, have fewer
Genetic Diversity
- The variety of alleles within a species
- Each species is made up of individuals that have their own particular genetic composition.
- This means a species may have different populations, each having different genetic compositions
Variation in ecosystems or habitats
- Ecosystem diversity is the variety of ecosystems in given place
- An ecosystem is a community of organisms and their physical environment interacting together
- An ecosystem can cover a large area, such as a whole forest, or a small area, such as a pond
Abiotic Factors
non-living chemical and physical factors in the environment which affect ecosystems
Biotic Factors
a living component of an ecosystem; for example organisms, such as plants and animals
Stratified Sampling
- Stratified sampling is simply the process of identifying areas within an overall habitat, which may be very different from each other and which need to be sampled separately.
- Each individual area separately sampled within the overall habitat is then called a stratum.
- The habitat may be fairly uniform, in which case, this is unnecessary
- Within stratified sampling, there is random sampling and systematic sampling
Random Sampling
Used when an area looks reasonably uniform, or if there is no clear pattern to the way species are distribute
- like by using a random number generator
- the random numbers give you the coordinates of the sampling points in relation to the two tapes you have used to mark out the area
Quadrat
a square frame that marks off an area of ground, or water, where you can identify the different species present and/or take a measurement of their abundance
- no use for counting animals
Why take random samples?
- To remove observer bias in the selection of samples.
- Where statistical tests are to be used which require randomly collected data.
- Where a large area needs to be covered quickly.
- If time is very limited.
Using a frame quadrat to estimate species frequency
a measure of the chance of a particular species being found within any one quadrat
- you simply record whether the species was present in each quadrat that you analyse
- like out of 50 times you see the same species 22 times so the species frequency is 22/50 = 44%
Using a frame quadrat to estimate percentage cover species density
a measure of how many individuals there are per unit area – for example, per square metre.
- The number of individuals that you have counted is divided by the total area of all your quadrats
Using a frame quadrat to estimate percentage cover
- not always possible to count individual plants and animals because of the way that they grow
- sometimes it is impossible to count individuals
- you can use a 100 cm × 100 cm quadrat with wires running across it at 10 cm intervals in each direction, dividing the quadrat into 100 smaller squares.
- you then decide approximately what percentage of the area inside the quadrat is occupied by each species
Estimating number of mobile animals
Small mammals, such as mice and voles, can be caught in traps that are filled with hay for bedding and suitable food as bait
- The techniques for this vary according to the size of the body of water, and whether it is still or moving
- Method –> mark-release-recapture technique
Mark–release–recapture technique
1) As many individuals as possible are caught. Each individual is marked, in a way that will not affect its future chance of survival
2) The marked individuals are counted, returned to their habitat and left to mix randomly with the rest of the population
3) When enough time has elapsed for the mixing to take place, another large sample is captured.
4) The number of marked and unmarked individuals is counted.
5) The proportion of marked to unmarked individuals is then used to calculate an estimate of the total number in the population
Estimating population in the Mark–release–recapture technique
- Estimate population by multplying number caught and marked in 1st sample with number caught in 2nd sample.
- Then divide the whole thing by the number in the second sample that had been marked
Simpson’s Index of Diversity
used to calculate a value for the species diversity in that area, once information is collected
D = 1 − ∑ ( ( n / N ) ^2 )
- n is the total number of organisms of a particular species
- N is the total number of organisms of all species
Simpson’s Index of Diversity values
- Values of D range from 0 to 1.
- A value near 0 represents a very low species diversity. - A value near 1 represents a very high species diversity
- diversity depends on the number of different species there are, and also the abundance of each of those species